To mix more realistic greens (like those in landscapes), often the intensity needs to be modified. Here is a mixing exercise that changes the intensity of the greens without changing its value..
First: Mix more cadmium yellow pale (top first row) with less ultramarine blue (second box: first row) to achieve a nice starting "cinnabar light" green (warm, opaque, spring green: top: second row). Then, alter the values of the greens: in order, these are: add more ultramarine blue (darker), original mix, add more cadmium yellow light and more cadmium yellow light. Above: instead of yellow, add more white and more white.
To achieve the slightly less intense (but same value greens seen in the row beneath these starting greens, first mix equal value violets to the greens that will be modified.
Violet is made with ultramarine blue (second box: first row) and permanent rose (third box: first row). It is more red (third box: second row) or more blue( second box, second row) violet, depending on which is the predominant color in the mixture. Both mixed purples (the reddish and the bluish) are dark colors so to determine what a dark mixed color looks like, test a tiny piece of it by adding white (shown third row beside parent dark purples). To change the values of the purples, add white (string of purples beneath matched value greens).. The slightly less intense greens are made by adding a tiny amount of the corresponding value-matched purple into the green that is being dulled down. Adding MORE purple, will grey the green further. By first making a matched value of violet, the mixed green will keep its value and change only its intensity. A small amount of the matched blue or red violet was added to the greens lightened with white in the top right squares.
Do this yourself. It will make more sense. this exercise will also be practice for making some good starting greens and violets.
Bright unmodified greens in this floral study. This painting was working on bright, not realistic colors.